/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package io.delta.flink.internal.lang;

import java.util.Optional;
import java.util.function.Supplier;

public class Lazy<T> {
    private final Supplier<T> supplier;
    private Optional<T> instance = Optional.empty();

    public Lazy(Supplier<T> supplier) {
        this.supplier = supplier;
    }

    /** Not thread safe. */
    public T get() {
        if (!instance.isPresent()) {
            instance = Optional.of(supplier.get());
        }
        return instance.get();
    }
}
